Fs90r wont take throttle

Gramp75

Gramp75

Forum Newbie
IAdjusting jets no help it runs starts but wont take throttle. Valve lash looks good. Right now im running bare carb covers and air cleaner missing. Opened carb all looks cleangood. Too things i noticed. Carb is spitting and when idling its rough like rich but every so often it smooths out for a second only. No idea what the bottom diaphram thing does one carb with big hose to motor? Also dont know jet settings. And whats that doohickey on top of gas tank under carb?
 

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Hammermechanicman said:
Have you checked the exhaust screen?
The doohickey is the tank vent.
Click to expand...
It runs shoots smoke out exhaust. Th priblem i think is the gas spitting outcarb at idle. Idle is consistant but acts like every other spark fire. Other thing is jets dont effect it but carb is clean inside
 
First you should not be able to adjust much with the limiter caps in place. How is the metering diaphragm? Is it stiff?

Also have you adjusted the valves? And have you checked the spark arrester?
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Pull the muffler. Clean out the exhaust port and muffler screen as suggested previously. Rebuild the carb.
 
I see no comments about carb spitting has to be valve timing or valve fault. Like worn guide? Or cam shaft defect? I may pull muffler for kicks. Who knows? Gaskets diaphrams are good. This unit looks like its got a million miles on it.
 
If it is spitting back fuel at idle the first thing to check is the exhaust screen being plugged. On a 4 mix the next thing is valve adjustment. If engine has a lot of hours on it and not run hard enough to keep it up to temp it can be carboned up to the point intake valve not sealing properly. Stihl sells an expensive can of stuff that will decarbon an engine.
 
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